1. Field of the Invention
This invention relates to a data communication system, and more particularly, to a data communication system for performing data communication between a host computer and a portable terminal.
2. Description of the Related Art
In a data communication system for performing data communication between a host computer and a portable terminal, it is common to provide an electronic apparatus for intermediation which is connected to the host computer and which can be connected to the portable terminal, and when starting communication between the host computer and the portable terminal, the procedure is to turn on a power supply switch of the electronic apparatus for intermediation, connect the portable terminal to the electronic apparatus for intermediation, and perform an instruction for starting communication from the portable terminal to the host computer by a key input on the portable terminal. After a communication state has been thus established, communication has been performed and communication has been completed, the connection of the portable terminal is disconnected, and the power switch is then turned off to terminate a series of operations for communication. In the above-described configuration, however, the power supply switch of the electronic apparatus for intermediation must be turned on and off at starting and terminating communication. This is a troublesome operation. If the power supply of the electronic apparatus is always kept turned on in order to avoid the troublesome operation, electric power is wasted. Alternatively, it often occurs that the operator forgets to turn off the power supply switch after terminating communication, and electric power is wasted also in this case.
Moreover, since it is necessary to perform a key input for instructing the start of communication from the portable terminal connected to the electronic apparatus, it becomes impossible to perform communication if the user does not understand the instructing operation for starting or has forgotten it. Particularly in an interactive system in which various operations are instructed for the user, once communication has been started the subsequent operations can be executed according to instructions from the host computer. The operation for starting communication, however, must be performed by the user himself without aid of the host computer.
If the electronic apparatus for intermediation is always kept in a communicating state in order to avoid the above-described problems, the number of electronic apparatuses for intermediation which can communicate with the host computer is remarkably limited.